International Journal of Sediment Research
Volume 31, Issue 3, Pages 195-278 (Sep. 2016)
Managing reservoir sedimentation by venting turbidity currents: A review
Pages 195-204
Sabine Chamoun, Giovanni De Cesare, Anton J. Schleiss
A study on limit velocity and its mechanism and implications for alluvial rivers
Pages 205-211
Yanhong Jia, Zhaoyin Wang, Xiangmin Zheng, Yanfu Li
Impact of climate change on sediment yield for Naran watershed, Pakistan
Pages 212-219
Farooq Azim, Abdul Sattar Shakir, Habib-ur-Rehman, Afshan Kanwal
Critical caving erosion width for cantilever failures of river bank
Pages 220-225
Yangui Wang, Shangfu Kuang, Jialin Su
Distribution of trace metals and Pb isotopes in bottom sediments of the Murucupi River, North Brazil
Pages 226-236
Diomar Cavalcante Oliveira, Jean Michel Lafon, Marcelo de Oliveira Lima
Field measurements of settling velocities of fine sediments in Three Gorges Reservoir using ADV
Pages 237-243
Wenjie Li, Shengfa Yang, Jiang Hu, Xuhui Fu, Peng Zhang
Effect of pier shape and pier alignment on the equilibrium scour depth at single piers
Pages 244-250
Cristina Fael, Rui Lança, António Cardoso
Modification of the Engelund bed-load formula
Pages 251-256
Zhen Meng, Danxun Li, Xingkui Wang
Numerical modeling of sedimentation control scenarios in the approach channel of the Nakdong River Estuary Barrage, South Korea
Pages 257-263
Un Ji, Eun-Kyung Jang, Gwonhan Kim
Morph- and hydro-dynamic effects toward flood conveyance and navigation of diversion channel
Pages 264-270
Min Xu, Li Chen, Qihui Wu, Dongfeng Li
Listen to the sound of moving sediment in a small gravel-bed river
Pages 271-278
Andreas Krein, Reimar Schenkluhn, Andreas Kurtenbach, Reinhard Bierl, Julien Barrière
Full papers are available at ScienceDirect:
http://www.sciencedirect.com/science/journal/10016279,
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Sabine Chamoun, Giovanni De Cesare, Anton J. Schleiss, Managing reservoir sedimentation by venting turbidity currents: A review, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 195-204, ISSN 1001-6279,
http://dx.doi.org/10.1016/j.ijsrc.2016.06.001.
(http://www.sciencedirect.com/science/article/pii/S1001627916300385)
Abstract: Abstract
Reservoir sedimentation is an issue that dam operators are increasingly facing as dams are aging. Not only does it reduce a reservoir׳s capacity but it also affects its outlet structures such as bottom outlets and powerhouse intakes. Sedimentation may also impoverish downstream ecosystems. For these reasons, several strategies for sediment management are being investigated and applied worldwide. Among these methods, venting of turbidity currents reaching the dam can be very beneficial and economical. This measure helps in preserving a certain continuity of sediment transport in rivers obstructed by dams. However, several practical but also theoretical challenges hamper this technique, rendering its use less common and its aspects relatively unknown. The present paper aims to gather the actual state-of-the-art concerning turbidity currents venting and to present an outlook for future development and research in this field.
Keywords: Reservoir management; Sedimentation; Turbidity current; Venting efficiency; Bottom outlet
Yanhong Jia, Zhaoyin Wang, Xiangmin Zheng, Yanfu Li, A study on limit velocity and its mechanism and implications for alluvial rivers, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 205-211, ISSN 1001-6279,
http://dx.doi.org/10.1016/j.ijsrc.2015.01.002.
(http://www.sciencedirect.com/science/article/pii/S100162791500027X)
Abstract: Abstract
Observations from field investigations showed that flow velocity greater than 3 m/s rarely occurs in nature, and high flow velocity stresses the bio-community and causes instability to the channel. For alluvial rivers without strong human disturbance, the flow velocity varies within a limited range, generally below 3 m/s, while the discharge and wet area may vary in a range of several orders. This phenomenon was studied by analyzing hydrological data, including daily average discharge, stage, cross sections, and sediment concentration, collected from 25 stations on 20 rivers in China, including the Yangtze, Yellow, Songhua, Yalu, Daling, and Liaohe Rivers. The cross-sectional average velocity was calculated from the discharge and wet area using the continuity equation. For alluvial rivers, the wet cross section may self-adjust in accordance with the varying flow discharge so that the flow velocity does not exceed a limit value. In general, the average velocity increases with the discharge increase at low discharge. As the discharge exceeds the discharge capacity of the banks, any further increase in discharge does not result in a great increase in velocity. The average velocity approaches an upper limit as the discharge increases. This limit velocity, in most cases, is less than 3 m/s. Human activities, especially levee construction, disturb the limit velocity law for alluvial rivers. In these cases, the average velocity may be approximately equal to or higher than the limit velocity. The limit velocity law has profound morphological and ecological implications on alluvial rivers and requires further study. Rivers should be trained and managed by mimicking natural processes and meeting the limit velocity law, so as to maintain ecologically-sound and morphological stability.
Keywords: Limit velocity; Alluvial river; Self-adjustment; Wet area; Human activity
Farooq Azim, Abdul Sattar Shakir, Habib-ur-Rehman, Afshan Kanwal, Impact of climate change on sediment yield for Naran watershed, Pakistan, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 212-219, ISSN 1001-6279,
http://dx.doi.org/10.1016/j.ijsrc.2015.08.002.
(http://www.sciencedirect.com/science/article/pii/S1001627916300257)
Abstract: Abstract
In this paper, the site-specific impact of climate change on sediment yield has been assessed for the Naran watershed, Pakistan. Observed data has been gathered for period 1961–2010 and HaDCM3 GCM predictors of SRES scenarios A2 and B2 have been downloaded. Future precipitation and temperature time series have been statistically downscaled for time horizon 2011–2040 and 2041–2070. Downscaled data show both increasing and decreasing changes with respect to the observation. Potential sediment yield for future related to climate change has been simulated. The results show that the both snowy and monsoon seasonal stream discharges are expected to increase. This will lead to increase in annual suspended sediment yields. Percentage-wise, a less discharge and more sediment yield are expected during the early summer. The study concluded that the climate change and variability are influencing the watershed, and suspended sediment yield is likely to increase in the future.
Keywords: Climate change; Downscaling; Hydrologic modeling; Suspended sediment yield; SHETRAN
Yangui Wang, Shangfu Kuang, Jialin Su, Critical caving erosion width for cantilever failures of river bank, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 220-225, ISSN 1001-6279, http://dx.doi.org/10.1016/j.ijsrc.2016.05.003.
(http://www.sciencedirect.com/science/article/pii/S1001627916300269)
Abstract: Abstract
The cantilever failure is one of the typical bank failures, in which the lateral caving erosion at the bottom of the bank plays an important role. When the caving erosion width is larger than a certain value, the cantilever failures such as shear, toppling and stress failures may occur. In order to understand the condition of the cantilever failure, the collapse mechanisms of the cantilever failures are studied based on the bank stability theory and flume experiment. According to the bank stability equation with the lateral erosion, the critical caving erosion width (CCEW) formulas for the shear and toppling failures of simple slope bank were derived in this paper. The formulas show that the CCEW increases as the overhanging soil thickness and soil cohesion increase, and decreases as the crack depth on the bank surface and the slope angle of the bank increase. And these formulas were tested with experimental data, which shows the predicted values are good agreement with experimental data. The paper reveals a quantitative expression on the process of the river cantilever failure.
Keywords: Caving erosion; Cantilever failure; Stability coefficient; Critical caving erosion width
Diomar Cavalcante Oliveira, Jean Michel Lafon, Marcelo de Oliveira Lima, Distribution of trace metals and Pb isotopes in bottom sediments of the Murucupi River, North Brazil, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 226-236, ISSN 1001-6279, http://dx.doi.org/10.1016/j.ijsrc.2016.05.001.
(http://www.sciencedirect.com/science/article/pii/S1001627916300233)
Abstract: Abstract
The Murucupi River belongs to the hydrographic network of the Pará River estuary, at the southern portion of the Amazon River mouth, which consists of a fluvial-marine transitional zone under strong impact of both tidal and fluvial currents. The geochemical results obtained for bottom sediments from the Murucupi River, the Arrozal Channel, and the Pará River indicate a natural variation of Pb, Cr, Cu, Zn, and Ni content among these water ways with no significant anthropogenic influence. According to the threshold effects level (TEL), the contents of trace metals do not offer risk to the local biota. By contrast, the differences in the Pb isotopic composition of sediments in the Murucupi River, the Arrozal Channel, and the Pará River are significant. These isotopic signatures indicate an anthropogenic contribution of Pb in the Murucupi River originating from the domestic effluents of urban centers; industrial waste represented by red mud is not included. These results demonstrate that the Pb isotopic signature is a prospective indicator for future contamination of bottom sediments by trace metals and is useful for identifying contaminants among the possible anthropogenic sources.
Keywords: Bottom sediments; Pb isotopes; Trace metals; Murucupi River; Barcarena
Wenjie Li, Shengfa Yang, Jiang Hu, Xuhui Fu, Peng Zhang, Field measurements of settling velocities of fine sediments in Three Gorges Reservoir using ADV, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 237-243, ISSN 1001-6279,
http://dx.doi.org/10.1016/j.ijsrc.2016.05.002.
(http://www.sciencedirect.com/science/article/pii/S1001627916300245)
Abstract: Abstract
The Three Gorges Reservoir (TGR) is suffering from unexpected fine sediment deposition, to better understand the fine sediment transport processes, field measurements were conducted at the Zhongxian and Fengjie reaches. A method based on the sediment diffusion equation was proposed to measure the settling velocities using the Acoustic Doppler Velocimeter (ADV). The backscatter acoustic intensities (BSI) received from the ADV were calibrated against the sediment concentrations measured via water sampling, suggesting a linear relationship in double logarithmic coordinate system. The instantaneous sediment concentration was calculated using the derived relationship, and then the settling velocity was obtained through the proposed procedure. The settling velocities of the fine particles in the TGR were found to vary with the water depth. Most of the effective settling velocities were within the range of 0.1–10 mm/s, which were larger than those of the primary particles, indicating that the flocculation was likely to occur in the TGR. Additionally, it is suggested that the turbulent motion played an important role in the flocculation in the TGR.
Keywords: Settling velocity; Fine sediments; Acoustic Doppler Velocimeter; Field measurement; Three Gorges Reservoir
Cristina Fael, Rui Lança, António Cardoso, Effect of pier shape and pier alignment on the equilibrium scour depth at single piers, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 244-250, ISSN 1001-6279,
http://dx.doi.org/10.1016/j.ijsrc.2016.04.001.
(http://www.sciencedirect.com/science/article/pii/S1001627916300142)
Abstract: Abstract
The equilibrium scour depth at uniform single bridge piers depends on a large number of variables, including the pier horizontal cross-section shape and its alignment angle towards the flow direction. The influence of these variables has been studied by only a few researchers, mostly, on the basis of tests that were far from approaching equilibrium. This experimental study aims at revisiting the influence of piers׳ shape and alignment on local scouring for length–width ratios smaller than or equal to 4, by increasing the experimental evidence. Fifty five long-duration laboratory tests were run under steady, clear-water flow, close to the threshold for initiation of sediment motion. Five pier shapes were considered: circular, rectangular square-nosed, rectangular round-nosed, oblong, and zero-spacing (packed) pile-groups; the tested skew-angles were 0°, 30°, 45°, 60°, and 90°. It was concluded that i) the shape factor can be taken as 1.0, for rectangular round-nosed and oblong cross-section piers, and as 1.2, for rectangular square-nosed and packed pile-group cross-section piers, ii) the shape factor does not vary significantly with the duration of tests, this way confirming the robustness of the shape factors reported to date, iii) the effect of shape is present at skewed piers although the associated coefficients remain in the narrow range of 1.0–1.2, and iv) for length–width ratios smaller than 4, the shape factor is of the same order of magnitude as the skew angle factor and should not be neglected.
Keywords: Scour; Pier shape; Pier alignment
Zhen Meng, Danxun Li, Xingkui Wang, Modification of the Engelund bed-load formula, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 251-256, ISSN 1001-6279,
http://dx.doi.org/10.1016/j.ijsrc.2015.09.002.
(http://www.sciencedirect.com/science/article/pii/S1001627916300221)
Abstract: Abstract
The classic Engelund bed-load formula involves four oversimplified assumptions concerning the quantity of particles per unit bed area that can be potentially entrained into motion, the probability of sediment being entrained into motion at a given instant, the mean velocity of bed-load motion, and the dimensionless incipient shear stress. These four aspects are reexamined in the light of new findings in hydrodynamics, and a modified bed-load formula is then proposed. The modified formula shows promise as being reliable in predicting bed-load transport rates in a wide range of flow intensities.
Keywords: Bed-load transport; Incipient shear stress; Entrainment probability; Flow intensity
Un Ji, Eun-Kyung Jang, Gwonhan Kim, Numerical modeling of sedimentation control scenarios in the approach channel of the Nakdong River Estuary Barrage, South Korea, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 257-263, ISSN 1001-6279, http://dx.doi.org/10.1016/j.ijsrc.2016.02.001.
(http://www.sciencedirect.com/science/article/pii/S1001627916300014)
Abstract: Abstract
The effects of sedimentation reduction at the Nakdong River Estuary Barrage (NREB) in Korea were quantitatively analyzed with respect to different sediment control methods using the calibrated and validated two-dimensional model. The countermeasures of sediment dredging, sediment flushing, channel geometry change, and a combination of flushing and channel geometry change were examined for the approach channel of the NREB. The flood event and channel geometries of the 3.8 km section upstream of the NREB surveyed before and after dredging in 2007 were used for modeling conditions. As a result, the half of sediments dredged in 2007 could be eliminated naturally by floods without dredging. The numerical simulation of sediment flushing indicated that the deposition height decreased in the entire simulation section with the minimum and maximum reductions from 0.3 m to 1.3 m in deposition height. The channel contraction method produced quantitatively the largest amount of sedimentation reduction and sediment flushing and dredging followed. Sedimentation reduction by a combination of flushing and channel contraction was up 10% compared to the individual method of channel contraction.
Keywords: Channel contraction; Nakdong River Estuary Barrage; Sediment dredging; Sediment flushing; Sedimentation reduction
Min Xu, Li Chen, Qihui Wu, Dongfeng Li, Morph- and hydro-dynamic effects toward flood conveyance and navigation of diversion channel, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 264-270, ISSN 1001-6279,
http://dx.doi.org/10.1016/j.ijsrc.2015.09.001.
(http://www.sciencedirect.com/science/article/pii/S1001627915000669)
Abstract: Abstract
The functions of the diversion channel are usually disturbed by sediment erosion and deposition. Considering the effects of unsaturated sediment flow and narrowed cross section the diversion channel is enormously eroded. The discharge capacity, however, is deteriorated for the local deposition which lessens the water depth to satisfy the minimum navigable flow rate. In this study, the alternative diversion channel with unsaturated sediment flow at Hanjiang River, China, was taken as an example. The impacts of bed morphology for flood events and normal flow conditions were analyzed. The results show that the consideration of bed morphology is essential to design the diversion channel. Even for the unsaturated and eroded channel, the local deposition can reduce the water depth and restrict the navigable requirement under normal flow conditions.
Keywords: Diversion channel; Bed morphology; Navigation condition; Discharge capacity; Channel design
Andreas Krein, Reimar Schenkluhn, Andreas Kurtenbach, Reinhard Bierl, Julien Barrière, Listen to the sound of moving sediment in a small gravel-bed river, International Journal of Sediment Research, Volume 31, Issue 3, September 2016, Pages 271-278, ISSN 1001-6279,
http://dx.doi.org/10.1016/j.ijsrc.2016.04.003.
(http://www.sciencedirect.com/science/article/pii/S1001627916300178)
Abstract: Abstract
In order to assess the dynamics of rivers, a reliable characterization of bedload transport particularly during unsteady flow regimes is required. In contrast to highly energetic cases in hillslope areas, we aim to answer the question whether the usage of acoustic measurements can improve the characterization of bedload in small rivers draining low land mountains with comparatively low water discharge and bedload. In addition to the investigation of natural flood events, controlled floods were generated by releasing water from a reservoir into a small gravel-bed stream. The controlled releases allow for an evaluation of bedload solely from channel storage or bank erosion. For acoustical in-situ characterization of bedload transport, hydrophones were mounted onto the bottom side of steel plates, thus recording the impacts of sediments via the acoustic vibrations on the surface of the plates while at the same time minimizing the disturbing noise resulting from water turbulence. Corresponding bedload traps are removable boxes with open lids fixed in the riverbed so that bedload material registered by the hydrophone is trapped. The acoustic signals correlate well with the quantity of the transported material. During summer flood events the highest transport rates occur at the beginning of the rising limb featuring clockwise hysteresis. This is due to the rising transport energy of the flow and the presence of loose, unconsolidated material. During typical winter flood events bedload shows anticlockwise loops. The intensification of bedload conveyance after the runoff peak can be explained by a decreasing stability of the bed material from the beginning to the end of a transport event. Anticlockwise behavior also results from a combination of bedload exhaustion in the vicinity of the monitoring station with a delayed arrival of new material from distal sources later in the hydrograph.
Keywords: Bedload; Gravel-bed; Hydroacoustic; Hysteresis; Plate system